In large refrigeration systems, for example those used in the industrial field, correspondingly large valves are required; each of whose valve elements is activated from the outside by a control motor. When displacing the valve element, a passage through the valve is further released or further throttled. Such a valve can also be closed. In this case, the valve element bears on a valve seat.
In refrigeration systems, it is endeavoured to prevent the loss of refrigerant. When a system is filled with a combustible refrigerant, the loss of refrigerant can lead to dangerous situations. When ammonia is used as refrigerant, the escape of refrigerant will cause unpleasant smells. Large amounts of ammonia are also lethal. With refrigerants having a higher price, for example H-FCKW or H-FKW, refrigerant losses are expensive.
Weak spots with respect to sealing refrigeration systems are those places, in which a lead-through extending into a housing is required, for example to drive a valve element from the outside. Locating a control motor inside a refrigeration system is not always possible, as some refrigerants act aggressively upon electrical motors. Accordingly there is a need for a valve that can be driven without having to create a weak spot.
Another difficulty associated with valves of the above-described type occurs as a result of control motor failure. When this occurs, it is possible for the valve to remain in the position it was in when the motor failed. This may be a very undesirable position that could result in a loss of ability to properly control the refrigeration system. Accordingly, there is a need for an appropriate fail-safe mechanism to be associated with the valve.
Based on the foregoing, the general object of the present invention is to provide a fail-safe valve that improves upon or overcomes the problems and drawbacks of the prior art.